One of the interests in studying the intercalation phenomenon of Li-ion is to explain the hystereses which are observed on the open circuit voltage curve of the graphite electrode during the charge and discharge. We investigated a potentiometric method to obtain the equilibrium curve and entropy change curve of the graphite electrode in charge and discharge. These curves lead to the analysis of the intercalation compounds in the graphite electrode. The results show a high hysteresis between the lithiation and delithiation in region II on the entropy curve. We do not observe the formation of LiC 18 compound which would be observed at filling fraction x = 0.33 and there is no clear evidence of the LiC 27 at x = 0.22. Based on our observations, we propose an intercalation model of Li into graphite in an attempt to explain the hysteresis phenomenon which was observed during charge and discharge in region II due to the possible presence of the compound LiC 24 . We have also observed a possible compound for the LiC 24 by XRD post-mortem analysis. With the significant growth of renewable energies, Li-ion batteries are going to play an increasing important role in energy storage systems. In Li-ion batteries, the material used for the anode is mainly graphite carbon for the following reasons: low cost, safety, capacity, cyclability and redox potential. The graphite of the negative electrode is prone to degradations such as solid electrolyte interphase formation (SEI), dendrites formation and Li plating on the surface. These mechanisms increase battery ageing and seriously reduce the performance and lifespan.1 It is interesting to study intercalation effects of Li-ion to understand the Li intercalation mechanisms in the crystal structure of the graphite and to explain the hystereses which are observed between the charge and discharge processes.2,3 The analysis of the open circuit voltage (OCV) curve and entropy curve of the electrode material highlights the crystallographic phases of the compounds inserted into graphite. In the following study, we focus our investigations on the transition phase in the regions II and III (Figure 7) in an attempt to explain the high hysteresis which was more specifically observed on the entropy curve of the negative electrode.The graphite presents a planar hexagonal structure and the stacking is A-B-A-B. 4 The dynamic of intercalation of Li-ions into graphite creates disorder within the crystal structure. The entropy variation S during the chemical reaction is reflected in the degree of disorder in the active material. When a crystal structure is achieved, it corresponds to a crystallographic phase. 5 The electrode charges and discharges according to the various insertion stages (Figure 1), this representation is based on the Daumas-Hérold intercalated model. 6 The graphite stage corresponds to the natural carbon graphite when the electrode is empty of Li. During the insertion reaction, the graphite is loading in Li through several stages. The stages are defined according to the number of ...

This paper describes the statistical analysis of recorded data parameters of electrical battery ageing during electric vehicle use. These data permit traditional battery ageing investigation based on the evolution of the capacity fade and resistance raise. The measured variables are examined in order to explain the correlation between battery ageing and operating conditions during experiments. Such study enables us to identify the main ageing factors. Then, detailed statistical dependency explorations present the responsible factors on battery ageing phenomena. Predictive battery ageing models are built from this approach. Thereby results demonstrate and quantify a relationship between variables and battery ageing global observations, and also allow accurate battery ageing diagnosis through predictive models.

-In recent years, Li-ion batteries have been proposed as an essential element for hybrid electrical vehicles (HEV) and electrical vehicles (EV). In such applications, the most possible accurate estimation of the battery states is needed to optimize its operation. Accordingly, battery electrical impedance is known to be able to provide useful states information. Though that electrical impedance spectroscopy has firmly established itself as one of the most informative investigation method especially because of its accuracy, it cannot be easily implemented in embedded systems. In this paper, broadband excitation signals, frequently used in system identification applications, are proposed to perform impedance measurements on a battery cell. Moreover, spectral coherence is an advanced parameter estimated in order to determine the frequency bands where the transfer function of the system is accurately identified. We propose in this study to test and compare the identification performances of such signals for the broadband monitoring of a battery.